Study On The Effect Of Heat Transfer On The Stability Of Pulse Combustion

Micro-burner is the core component of power micro electromechanical systems and the existing micro-burner are developed on continuous combustion. Where the microscale effects, cause problems like combustion instability, incomplete combustion, low combustion efficiency and thermal efficiency, and high pollutant emissions. Pulse combustion has the advantage of high efficiency and intensity, high thermal efficiency, low pollution emission, which may be applied to overcome the existing problems of the micro-combustor. In this thesis, a micro-pulsating combustion technology concept was proposed and its feasibility was verified through experimental study.This paper aimed at Rijke pulse combustor of small diameter and study operation frequency, tability, signal to noise ratio and heat transfer characteristic in different heat transfer condition. From the experiment we get follow results:1. Rijke pulse combustor can work only if the follow criteria are satisfied:combustion position is the half bottom of tube, gas velocity in the tube must get a specific value, combustion thermal must arrive at specific intensity.2. Among operation process frequency hopping is happened in pulse combustor and the heat transfer in the bottom of tube can increase frequency content. According to frequency characteristic, the operation condition can classify to four parts:low-frequency region, high-frequency region, high harmonic region, turbulence region. Quartz tube pulse combustor in turbulence region may appear flameout, but the stainless steel tube pulse combustor did not happen this phenomenon.3. Experiment plot the stability figure of pulse combustor in different tube diameter, heat transfer condition and burner height. The figure show that:the smaller the tube diameter, the lower the combustion position is, the range of gas flux is more, and the operation is more stable. As the heat transfer out of the Rijke tube increase, the minimum flux of propane needed for oscillation starting also increase, the maximum flux of propane needed for frequency hopping and pulsation ending increase too, all this guarantee the stability of combustor.4. From the research on signal to noise ratio can know that signal to noise ratio did not increase simply with propane flux (power), it will increase for periods and then decrease, signal to noise ratio reach to the maximum value at specific flux and "heat source power saturation" is happened. The signal to noise ratio decrease gradually with the increment of heat transfer out Rijke tube and burner height.5. At the aspect of heat transfer efficiency, it is in direct proportion to pulse frequency and vibration intensity. increment of air and propane flux will weaken the bad effect of pulse frequency and vibration intensity on thermal efficiency.